Wireless communication device and power measurement device equipped with the same

ABSTRACT

A semiconductor device includes a semiconductor chip. The semiconductor chip includes: a switching-type DC-DC converter; a pad for receiving a high frequency signal from an antenna; a balun connected to the pad and configured with a coil to output a differential signal based on the high frequency signal; an internal circuit driven by an output voltage of the DC-DC converter to process the differential signal output from the balun; and a ground voltage line that couples the internal circuit to a ground voltage source. The ground voltage line includes a first partial ground voltage line, and a second partial ground voltage line arranged to face the first partial ground voltage line with the balun interposed therebetween.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a Continuation Application of U.S. patentapplication Ser. No. 15/498,276, filed on Apr. 26, 2017, which is basedon Japanese Patent Application No. 2016-135769 filed on Jul. 8, 2016including the specification, drawings and abstract is incorporatedherein by reference in its entirety.

BACKGROUND

The present invention relates to a wireless communication device and apower measurement device equipped with the same. For example, thepresent invention relates to a wireless communication device suitablefor receiving a high frequency signal with a high sensitivity, and apower measurement device equipped with such a wireless communicationdevice.

The wireless communication device includes a voltage generation unitthat generates voltage supplied to each functional block. In recentyears, LDO regulator has been replaced by a DC-DC converter as a voltagegeneration unit in order to reduce power consumption and externalcomponent cost. However, when the DC-DC converter is provided in thewireless communication device, a harmonic component (noise) generateddue to the switching operation of the DC-DC converter is propagated to abalun whose function is to output a differential signal based on awirelessly received high frequency signal, through a ground voltageline. As a result, there has been a problem that the receptionsensitivity of the high frequency signal is degraded at a specificfrequency of the wireless communication device.

For example, Patent Document 1 (Japanese Unexamined Patent ApplicationPublication No. 2000-286385) discloses the configuration of asemiconductor integrated circuit in which a shield metal layer fixed atthe grand level is laminated between a semiconductor substrate and asignal wiring layer. This configuration prevents the propagation ofnoise from the semiconductor substrate to the signal wiring layer.

SUMMARY

When the shield metal layer described above is applied to a wirelesscommunication device equipped with a DC-DC converter, a harmoniccomponent (noise) generated due to the switching operation of the DC-DCconverter is propagated to the shield metal layer fixed at the groundlevel through the ground voltage line, which is then propagated to thebalun. In other words, the shield metal layer may not prevent theharmonic component generated due to the switching operation of the DC-DCconverter from being propagated to the balun. As a result, there hasbeen a problem that the reception sensitivity of the high frequencysignal is degraded at a specific frequency of the wireless communicationdevice. These and other objects and novel features of the presentinvention will become apparent from the specification and theaccompanying drawings.

According to an embodiment, a wireless communication device isconfigured with a switching-type DC-DC converter and a coil. Thewireless communication device includes: a balun that outputs adifferential signal based on a wirelessly received high frequencysignal; an internal circuit that is driven by an output voltage of theDC-DC converter to process the differential signal output from thebalun; and a ground voltage line that couples the internal circuit to aground voltage source. The ground voltage line includes a first partialground voltage line, as well as a second partial ground voltage linearranged to face the first partial ground voltage line with the baluninterposed therebetween.

According to another embodiment, a wireless communication device isconfigured with a switching-type DC-DC converter, an internal circuitthat is driven by an output voltage of the DC-DC converter to output adifferential signal, and a coil. The wireless communication deviceincludes a balun that outputs a high frequency signal based on adifferential signal, and a ground voltage line that couples the internalcircuit to a ground voltage source. The ground voltage line has a firstpartial ground voltage line, as well as a second partial voltage linearranged to face the first partial ground voltage line with the baluninterposed therebetween.

According to the above described one embodiment, it is possible toprovide a wireless communication device that can receive a highfrequency signal with a high sensitivity by reducing the noise receivedfrom the DC-DC converter, as well as a power measurement device equippedwith such a wireless communication device.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing a configuration example of a wirelesscommunication system according to a first embodiment;

FIG. 2 is a schematic plan view of the wireless communication systemaccording to the first embodiment;

FIG. 3 is a schematic plan view showing the propagation of noise fromthe DC-DC converter to the balun in the wireless communication systemshown in FIG. 2;

FIG. 4 is a schematic plan view showing a variation of the wirelesscommunication system shown in FIG. 2;

FIG. 5 is a schematic plan view of a wireless communication systemaccording to a second embodiment;

FIG. 6 is a block diagram showing a configuration example of a wirelesscommunication system according to a third embodiment;

FIG. 7 is a schematic plan view of the wireless communication systemshown in FIG. 6;

FIG. 8 is a schematic plan view showing the propagation of noise fromthe DC-DC converter to the balun in the wireless communication systemshown in FIG. 7;

FIG. 9 is a schematic plan view of the wireless communication systemaccording to the idea before reaching the first embodiment;

FIG. 10 is a schematic cross-sectional view showing the propagation ofnoise from the DC-DC converter to a low noise amplifier in the wirelesscommunication system shown in FIG. 9;

FIG. 11 is a schematic cross-sectional view showing the propagation ofthe noise from the DC-DC converter to the low noise amplifier in thewireless communication system shown in FIG. 9;

FIG. 12 is a schematic cross-sectional view showing the propagation ofthe noise from the DC-DC converter to the low noise amplifier in thewireless communication system shown in FIG. 9; and

FIG. 13 is a schematic plan view showing the propagation of the noisefrom the DC-DC converter to the balun in the wireless communicationsystem shown in FIG. 9.

DETAILED DESCRIPTION

Hereinafter, preferred embodiments of the present invention will bedescribed with reference to the accompanying drawings. Note that thedrawings are simplified, so that the technical scope of the embodimentsshould not be construed narrowly on the basis of these drawings.Further, the same parts are designated by the same reference numerals,and the repetitive description thereof will be omitted.

In the embodiment described below, the detailed description of theinvention will be divided into a plurality of sections or embodimentswhen required as a matter of convenience. However, these sections orembodiments are not irrelevant to each other unless otherwise stated,and one serves as a variation, a detailed description, or asupplementary explanation of a part or the whole of the other. Also, inthe embodiment described below, when referring to the number of elements(including the number of pieces, numerical value, amount, range, etc.),the number of elements is not limited to a specific number unlessotherwise stated or it is clearly limited to a specific number inprinciple. The number of elements can be greater or smaller than thespecific number.

Further, in the embodiment described below, the components (includingoperation steps, etc.) are not necessarily indispensable, unlessotherwise stated or unless it is considered to be clearly indispensablein principle. Similarly, in the embodiment described below, whenreferring to the shape, the positional relationship, or othercharacteristics of the components, those practically approximating orcorresponding to the shape or other characteristics are included unlessotherwise stated or unless they are clearly considered not to be so inprinciple. This is true for the number or other attributes (includingthe number of pieces, numerical value, amount, range, etc.).

First Embodiment

FIG. 1 is a block diagram showing a configuration example of a wirelesscommunication system SYS1 according to a first embodiment. The wirelesscommunication system SYS1 is applied, for example, to power measurementdevices such as a smart meter, mobile phones, or car navigation systems.In the wireless communication system SYS1 according to the presentembodiment, not only a balun and a low noise amplifier but also a DC-DCconverter is mounted on a semiconductor chip that configures thewireless communication system. Further, a ground voltage line thatcouples the low noise amplifier to a ground voltage source is branchedinto first and second partial ground voltage lines. The first and secondpartial ground voltage lines are arranged to face each other with thebalun interposed therebetween. With this configuration, the wirelesscommunication system SYS1 according to the present embodiment can makethe magnitudes of the noises received at one output terminal of thebalun and the other output terminal thereof from the DC-DC converterapproximately equal to each other. Thus, it is possible to reduce thedegradation of the reception sensitivity of the high frequency signal ata specific frequency. A detailed description is given below.

As shown in FIG. 1, the wireless communication system SYS1 includes atleast a wireless communication device (semiconductor device) 1 and anantenna A1. For example, the wireless communication device 1 is formedon a single semiconductor chip, including a balun 11, a low noiseamplifier (an internal circuit) 12, a demodulation unit 13, an ADconverter 14, a baseband processing unit 15, and a DC-DC converter 16.Note that the example of FIG. 1 shows a circuit of the reception pathprovided in the wireless communication device 1 but, of course, thecircuit of the transmission path can be provided in the wirelesscommunication device 1.

The balun 11 converts a single-ended high frequency signal, which iswirelessly received from outside through the antenna A1, into adifferential high frequency signal (differential signal). Note that thebalun 11 not only converts the single-ended high frequency signal into adifferential high frequency signal, but also outputs a differential highfrequency signal by transmitting the differential high frequency signalin some cases. Hereinafter, only the former case will be described as arepresentative example.

More specifically, the balun 11 includes a primary coil L11 and asecondary coil L12. One end of the primary coil L11 is coupled to theantenna A1, and the other end of the primary coil L11 is coupled to aground voltage terminal GND. One end of the secondary coil L12 iscoupled to a non-inverting input terminal (P-side terminal) of the lownoise amplifier 12, and the other end of the secondary coil L12 iscoupled to an inverting input terminal (N-side terminal) of the lownoise amplifier 12.

For example, when the wirelessly received high frequency signal has apositive amplitude, the current flows from one end to the other end ofthe primary coil L11. Then, a positive electromotive force is generatedin the secondary coil L12, according to the change in the current of theprimary coil L11. On the other hand, when the wirelessly received highfrequency signal has a negative amplitude, the current flows from theother end to one end of the primary coil L11. Then, a negativeelectromotive force is generated in the secondary coil L12, according tothe change in the current of the primary coil L11. As a result, anegative amplitude AC signal is generated at one end of the secondarycoil L12 and a positive amplitude AC signal is generated at the otherend of the secondary coil L12. In other words, differential highfrequency signals are output from one end to the other end of thesecondary coil L12.

Note that the configuration of the balun 11 is not limited to theconfiguration described above, and can be appropriately changed to otherconfigurations having an equivalent function. For example, the balun 11can not only convert between balance and imbalance of electrical signalsbut also have a function as a matching circuit that performs impedancematching.

The low noise amplitude 12 amplifies the differential high frequencysignal output from the balun 11 with low noise. Note that the low noiseamplifier 12 may not be provided if it is not necessary to amplify thehigh frequency signal. The demodulation unit 13 demodulates thedifferential high frequency signal, which is amplified by the low noiseamplifier 12, into a baseband signal. The AD converter 13 converts theanalog baseband signal into a digital baseband signal. The basebandprocessing unit 15 performs a predetermined process based on the digitalbaseband signal.

The DC-DC converter 16 has a switching-type circuit configuration. TheDC-DC converter 16 performs a switching operation synchronously with aclock signal CLK (not shown) to generate an output voltage Vout bystepping up or down an input voltage Vin that is supplied from a powersource (not shown). The output voltage Vout is supplied to each of thefunctional blocks (the low noise amplifier 12, the demodulation unit 13,the AD converter 14, the baseband processing unit 14, and the like) thatare provided in the wireless communication device 1.

In this way, the wireless communication system SYS1 drives therespective functional blocks by using the output voltage Vout from theDC-DC converter 16, thus causing current to be intermittently suppliedfrom the power source. As a result, the increase in power consumptioncan be suppressed.

Next, the planar structure of the wireless communication system SYS1 isdescribed.

(Preliminary Study by the Inventors)

Before giving a detailed description of the planar structure of thewireless communication system SYS1, the planar structure of a wirelesscommunication system SYS50 that the inventors have previously studied isfirst described with reference to FIG. 9.

FIG. 9 is a schematic plan view of the wireless communication systemSYS50 according to the idea before reaching the first embodiment. Asshown in FIG. 9, in the wireless communication system SYS50, asemiconductor package 101 (corresponding to the wireless communicationdevice) is formed on a board 100. A tab ground 102, which is a commonground voltage area, is formed within the semiconductor package 101.Then, a semiconductor chip 103 is formed on the tab ground 102. Notethat the tab ground 102 is coupled to the ground voltage source GNDthrough the board 100.

A plurality of functional blocks and a plurality of pads are arranged onthe semiconductor chip 103. In the example of FIG. 9, of the functionalblocks, only the balun 11, the low noise amplifier 12, and the DC-DCconverter 16 are shown, and similarly of the pads, only pads PDV1, PDG1,PDGs 11 to 13, PDP1, and PDN1 are shown.

The pads are arranged along the outer periphery on the semiconductorchip 103. The balun 11 is provided as close to the outer periphery aspossible on the semiconductor chip 103. In this way, the balun 11 canreceive high frequency signals from outside with a high sensitivity.

As described above, the balun 11 is configured with the primary coil L11and the secondary coil L12. In the example of FIG. 9, the primary coilL11 and the secondary coil L12 are arranged in a whorl-like pattern insuch a way that their outer periphery is rectangular in the same wiringlayer (however, in different wiring layers at the intersection).Further, in the example of FIG. 9, the primary coil L11 and thesecondary coil L12 are arranged symmetrically with respect to the X-X′axis as the symmetry axis.

One end of the primary coil L11 is coupled to the pad PDP1, and theother end of the primary coil L11 is coupled to the pad PDN1. The padPDP1 is coupled to an external connection terminal P1 of thesemiconductor package 101 through a bonding wire BWP1. The externalconnection terminal P1 is coupled to the antenna A1 through the board100. The pad PDN1 is coupled to an external connection terminal N1 ofthe semiconductor package 101 through the bonding wire BWN1. Then, theexternal connection terminal N1 is coupled to the ground voltage sourceGND through the board 100.

One end of the secondary coil L12 is coupled to the non-inverting inputterminal (P-side terminal) of the low noise amplifier 12, and the otherend of the secondary coil L12 is coupled to the inverting input terminal(N-side terminal) of the low noise amplifier 12.

Further, a ground voltage line W50 is provided on the semiconductor chip103 to couple the low noise amplifier 12 and the ground voltage sourceGND. More specifically, the ground voltage line W50 is arranged toextend from the voltage terminal on the low potential side towards thepads PDG11 to PDG13 through the wiring area between the balun 11 and theouter periphery of the semiconductor chip 103.

The pads PDG11 to PDG13 are coupled to the tab ground 102 which is thecommon ground voltage area within the semiconductor package,respectively, through the bonding wires BWG11 to BWG13.

The voltage terminal on the high potential side of the DC-DC converter16 is coupled to the pad PDV1, and the voltage terminal on the lowpotential side of the DC-DC converter 16 is coupled to the pad PDG1. Thepad PDV1 is coupled to an external connection terminal V1 of thesemiconductor package 101 through the bonding wire BWV1. The externalconnection terminal V1 is coupled to a power supply voltage source VDDthrough the board 100. The pad PDG1 is coupled to an external connectionterminal G1 of the semiconductor package 101 through the bonding wireBWG1. Then, the external connection terminal G1 is coupled to the groundvoltage source GND through the board 100.

Here, in the wireless communication system SYS50, a harmonic component(noise), which is generated due to the switching operation of the DC-DCconverter 16, is propagated to the balun 11 through the ground voltageline W50. This leads to a problem that the reception sensitivity of thehigh frequency signal at a specific frequency is degraded in thewireless communication system SYS50.

The mechanism that the reception sensitivity of the high frequencysignal is degraded at a specific frequency of the wireless communicationsystem SYS50 will be describe in detail below.

FIGS. 10 to 12 are schematic cross-sectional views showing thepropagation of noise from the DC-DC converter 16 to the low noiseamplifier 12 in the wireless communication system SYS50.

First, referring to FIG. 10, the harmonic component (noise), which isgenerated due to the switching operation of the DC-DC converter 16, ispropagated from the voltage terminal on the low potential side of theDC-DC converter 16 to the bonding wire BWG1 through the pad PDG1. Thenoise is propagated to a bonding wire BWG11 (or BWG12, BWG13) that iselectromagnetically coupled to the bonding wire BWG1. Then, the noise ispropagated to the voltage terminal on the low potential side of the lownoise amplifier 12 through the pad PDG11 (or PDG12, PDG13).

Further, referring to FIG. 11, the harmonic component (noise), which isgenerated due to the switching operation of the DC-DC converter 16, ispropagated from the voltage terminal on the low potential side of theDC-DC converter 16 to the board 100, through the pad PDG1, the bondingwire BWG1, and the external connection terminal G1 of the semiconductorpackage 101. The noise is further propagated to the voltage terminal onthe low potential side of the low noise amplifier 12, through the tabground 102, the bonding wire BWG11 (or BWG12, BWG13), and the pad PDG11(or PDG12, PDG13).

Still further, referring to FIG. 12, the harmonic component (noise),which is generated due to the switching operation of the DC-DC converter16, is propagated from the voltage terminal on the low potential side ofthe DC-DC converter 16 to the bonding wire BWG1 through the pad PDG1.The noise is propagated to a bonding wire of a peripheral circuitelectromagnetically coupled to the bonding wire BWG1. Then, the noise ispropagated to the voltage terminal on the low potential side of the lownoise amplifier 12 through the bonding wire BWG11 (or BWG12, BWG13) aswell as the pad PDG11 (or PDG12, PDG13).

In other words, the harmonic component (noise), which is generated dueto the switching operation of the DC-DC converter 16, is propagated tothe low noise amplifier 12 through the path through which the groundvoltage supplied to the DC-DC converter 16 is propagated, and throughthe path through which the ground voltage supplied to the low noiseamplifier 12 is propagated.

FIG. 13 is a schematic plan view showing the propagation of the noisefrom the DC-DC converter 16 to the balun 11 in the wirelesscommunication system SYS50.

As shown in FIG. 13, of the wiring paths from the low noise amplifier 12to the pads PDG11 to PDG13 around the balun 11, the ground voltage lineW50 is located in a first path (a path on the side closer to the outerperiphery of the chip) passing through one side of the balun 11.However, the ground voltage line W50 is not located in a second path (apath on the side farther from the outer periphery of the chip) passingthrough the other side of the balun 11.

Thus, the electromagnetic coupling strength between the ground voltageline W50 and the positive side (one end side of each of the coils L11and L12) of the balun 11 is greater than the electromagnetic couplingstrength between the ground voltage line W50 and the negative side (theother end side of each of the coils L11 and L12) of the balun 11. As aresult, the difference between the magnitude of the noise received atone output terminal of the balun 11 (namely, one end side of the coilL12) from the DC-DC converter 16 and the magnitude of the noise receivedat the other output terminal of the balun 11 (namely, the other end sideof the coil L12) may increase to exceed the allowable range. In thiscase, the noise from the DC-DC converter is not sufficiently reduced bythe compensation of the in-phase component using the balun 11. As aresult, there is a problem that the reception sensitivity of the highfrequency signal is degraded at a specific frequency (which is anintegral multiple of the switching frequency).

Thus, the wireless communication system SYS1 according to the firstembodiment was conceived that can prevent the degradation of the highfrequency signal at a specific frequency by devising the arrangement ofthe ground voltage line that couples the low noise amplifier 12 to theground voltage source GND to make the magnitudes of the noises receivedat one output terminal and the other output terminal of the balun 11from the DC-DC converter approximately equal to each other.

(Planar Structure of the Wireless Communication System SYS1 According tothe First Embodiment)

FIG. 2 is a schematic plan view of the wireless communication systemSYS1 according to the first embodiment.

As shown in FIG. 2, in the wireless communication system SYS1, thesemiconductor package 101 (corresponding to the wireless communicationdevice) is formed on the board 100. The tab ground 102, which is thecommon ground voltage area, is formed within the semiconductor package101. Then, the semiconductor chip 103 is formed on the tab ground 102.Note that the tab ground 102 is coupled to the ground voltage source GNDthrough the board 100.

A plurality of functional blocks and a plurality of pads are arranged onthe semiconductor chip 103. In the example of FIG. 2, of the functionalblocks, only the balun 11, the low noise amplifier 12, and the DC-DCconverter 16 are shown, and similarly of the pads, only the pads PDV1,PDG1, PDG 11 to PDG13, PDP1, and PDN1 are shown.

The plurality of the pads are arranged along the outer periphery on thesemiconductor chip 103. The balun 11 is provided as close to the outerperiphery as possible on the semiconductor chip 103. This configurationallows the balun 11 to receive the high frequency signal from outsidewith a high sensitivity.

The balun 11 is configured with the primary coil L11 and the secondarycoil L12 as described above. In the example of FIG. 2, the primary coilL11 and the secondary coil L12 are arranged in a whorl-like pattern insuch a way that their outer periphery is rectangular in the same wiringlayer (however, in different wiring layers at the intersection).Further, in the example of FIG. 2, the primary coil L11 and thesecondary coil L12 are arranged symmetrically with respect to the X-X′axis.

One end of the primary coil L11 is coupled to the pad PDP1, and theother end of the primary coil L11 is coupled to the pad PND1. The padPDP1 is coupled to the external connection terminal P1 of thesemiconductor package 101 through the bonding wire BWP1. The externalconnection terminal P1 is coupled to the antenna A1 through the board100. The pad PDN1 is coupled to the external connection terminal N1 ofthe semiconductor package 101 through the bonding wire BWN1. Then, theexternal connection terminal N1 is coupled to the ground voltage sourceGND through the board 100.

One end of the secondary coil L12 is coupled to the non-inverting inputterminal (P-side terminal) of the low noise amplifier 12, and the otherend of the secondary coil L12 is coupled to the inverting input terminal(N-side terminal) of the low noise amplifier 12.

Further, the ground voltage line W1 is provided on the semiconductorchip 103 to couple the low noise amplifier 12 and the ground voltagesource GND. More specifically, the ground voltage line W1 is arranged toextend from the voltage terminal on the low potential side of the lownoise amplifier 12 towards the pads PDG11 to PDG13 around the balun 11.

The pads PDG11 to PDG13 are coupled to the tab ground 102 which is thecommon ground voltage area within the semiconductor package 101,respectively, through the bonding wires BWG11 to BWG13.

The voltage terminal on the high potential side of the DC-DC converter16 is coupled to the pad PDV1, and the voltage terminal on the lowpotential side of the DC-DC converter 16 is coupled to the pad PDG1. Thepad PDV1 is coupled to the external connection terminal V1 of thesemiconductor package 101 through the bonding wire BWV1. The externalconnection terminal V1 is coupled to the power supply voltage source VDDthrough the board 100. The pad PDG1 is coupled to the externalconnection terminal G1 of the semiconductor package 101 through thebonding wire BWG1. Then, the external connection terminal G1 is coupledto the ground voltage source GND through the board 100.

Here, of the wiring paths from the low noise amplifier 12 to the padsPDG11 to PDG13 around the balun 11, the ground voltage line W1 islocated in a first path (the path on the side closer to the outerperiphery of the chip) passing through one side of the balun 11. At thesame time, the ground voltage line W1 is also branched into a secondpath (a path on the side farther from the outer periphery of the chip)passing through the other side of the balun 11.

Hereinafter, the ground voltage line W1 provided in the first pathpassing through one side of the balun 11 will be referred to as apartial ground voltage line W11, and the ground voltage line W1 providedin the second path passing through the other side of the balun 11 willbe referred to as a partial ground voltage line W12. At this time, thepartial voltage lines W11 and W12 are arranged to face each other withthe balun interposed therebetween.

In other words, the ground voltage line W1 including the partial groundvoltage lines W11 and W12, as well as the low noise amplifier 12 areprovided to surround the balun 11. Note that a joint part Q1 of theground voltage line W1 in which the ground voltages supplied through thepads PDG11 to PDG13 are gathered is located outside the line part of theground voltage line W1 surrounding the balun 11. At the same time, thejoint part Q1 is located on the symmetry axis (on the X-X′ axis) of thebalun 11.

With this configuration, the difference between the noise received atone output terminal (one end of the secondary coil L12) of the balun 11and the noise received at the other output terminal (the other end ofthe secondary coil L12) of the balun 11 is reduced to a value within apredetermined allowable range (ideally, reduced to the extent that thereis virtually no difference). Thus, the noise from the DC-DC converter 16is sufficiently reduced by the compensation of the in-phase componentusing the balun 11. As a result, the wireless communication system SYS1can prevent the degradation of the reception sensitivity of the highfrequency signal at a specific frequency (which is an integral multipleof the switching frequency).

FIG. 3 is a schematic plan view showing the propagation of the noisefrom the DC-DC converter 16 to the balun 11 in the wirelesscommunication system SYS1.

As shown in FIG. 3, the partial ground voltage lines W11 and W12 arearranged to face each other with the balun interposed therebetween. Withthis configuration, the electromagnetically coupling strength betweeneach of the partial ground voltage lines W11, W12 and the positive side(the path on one end side of each of the coils L11 and L12) of the balun11 and the electromagnetically coupling strength between each of thepartial ground voltage lines W11, W12 and the negative side (the path onthe other side of each of the coils L11 and L12) of the balun 11 areapproximately equal to each other. In this way, the difference betweenthe magnitude of the noise received at one output terminal of the balun11 from the DC-DC converter 16 and the magnitude of the noise receivedat the other output terminal of the balun 11 from the DC-DC converter 16is reduced to a value within a predetermined allowable range. Thus, thenoise from the DC-DC converter 16 is sufficiently reduced by thecompensation of the in-phase component using the balun 11. As a result,the wireless communication system SYS1 can prevent the degradation ofthe reception sensitivity of the high frequency signal at a specificfrequency (which is an integral multiple of the switching frequency).

Note that it is desirable that the distance between the partial groundvoltage line W11 and the balun 11 and the distance between the partialground voltage line W12 and the balun 11 are substantially the same.More specifically, it is desirable that the distance between the partialground voltage line W11 and the outer periphery of the coils L11 and L12that configure the balun 11, and the distance between the partial groundvoltage line W12 and the outer periphery of the coils L11 and L12 thatconfigure the balun 11 are substantially the same. Here, the phrase“substantially the same” means including not only the case in which thetwo distances are completely equal to each other, but also the case inwhich the two distances deviate from the state of being completely equalby an error. In this way, the difference between the magnitude of thenoise received at one output terminal of the balun 11 from the DC-DCconverter 16 and the magnitude of the noise received at the other outputterminal of the balun 11 from the DC-DC converter 16 is further reduced.As a result, the degradation of the reception sensitivity of the highfrequency signal is further reduced at a specific frequency of thewireless communication system SYS1.

Also it is desirable that the width of the partial ground voltage lineW11 and the width of the partial ground voltage line W12 aresubstantially the same. Further, it is desirable that the partial groundvoltage line W11 and the partial ground voltage line W12 are arrangedsymmetrically with respect to the balun 11 (with the X-X′ axis as thesymmetry axis). In this way, the difference between the magnitude of thenoise received at one output terminal of the balun 11 from the DC-DCconverter 16 and the magnitude of the noise received at the other outputterminal of the balun 11 from the DC-DC converter 16 is further reduced.As a result, the degradation of the reception sensitivity of the highfrequency signal is further reduced at a specific frequency of thewireless communication system SYS1.

As described above, in the wireless communication system SYS1, not onlythe balun 11 and the low noise amplifier 12 but also the DC-DC converter16 is mounted on the semiconductor chip 103 forming the wirelesscommunication system 1. Further, the ground voltage line W1 that couplesthe low noise amplifier 12 to the ground voltage source GND is branchedinto the partial ground voltage lines W11 and W12. Then, the partialground voltage lines W11 and W12 are arranged to face each other withthe balun 11 interposed therebetween. With this configuration, thewireless communication system SYS1 can make the magnitudes of thenoises, which are received at one output terminal and the other outputterminal of the balun 11 from the DC-DC converter 16, approximatelyequal to each other, thereby reducing the degradation of the receptionsensitivity of the high frequency signal at a specific frequency.

(Variation of the Wireless Communication System SYS1)

FIG. 4 is a schematic plan view showing a variation of the wirelesscommunication system SYS1 as a wireless communication system SYS1 a. Thewireless communication system SYS1 a is different in the wiring patternof the ground voltage line W1 compared with the case of the wirelesscommunication system SYS1.

More specifically, the ground voltage line W1 is coupled to the padsPDG11 to PDG13 in the wireless communication system SYS1, but in thewireless communication system SYS1 a, the ground voltage line W1 iscoupled only to the pads PDG11 and PDG12. With this configuration, thewireless communication system SYS1 a can improve the symmetry of thewiring pattern of the ground voltage line W1. In this way, thedifference between the magnitude of the noise received at one outputterminal of the balun 11 from the DC-DC converter 16 and the magnitudeof the noise received at the other output terminal of the balun 11 fromthe DC-DC converter 16 is further reduced. As a result, the degradationof the reception sensitivity of the high frequency signal is furtherreduced at a specific frequency.

Note that the wiring pattern of the ground voltage line W1 is notlimited to that shown in FIG. 4, and can be appropriately changed into awiring pattern that can improve the symmetry.

Second Embodiment

FIG. 5 is a schematic plan view of a wireless communication system SYS1b according to a second embodiment.

As shown in FIG. 5, in the wireless communication system SYS1 b, a powersupply voltage line W2 through which the output voltage Vout of theDC-DC converter 16 is propagated from the DC-DC converter 16 to the lownoise amplifier 12 is branched into partial power supply voltage linesW21 and W22. The partial power supply voltage lines W21 and W22 arearranged to face each other with the balun 11 interposed therebetween.

More specifically, of the wiring paths from the DC-DC converter 16 tothe low noise amplifier 12 around the balun 11, the power supply voltageline W2 is located in a first path (a path on the side closer to theouter periphery of the chip) passing through one side of the balun 11.At the same time, the power supply voltage line W2 is also branched intoa second path (a path on the side farther from the outer periphery ofthe chip) passing through the other side of the balun 11.

Hereinafter, the power supply voltage line W2 located in the first pathpassing through one side of the balun 11 will be referred to as thepartial power supply voltage line W21, and the second power supplyvoltage line W2 located in the second path passing through the otherside of the balun 11 will be referred to as the partial power supplyvoltage line W22. At this time, the partial power supply voltage linesW21 and W22 are arranged to face each other with the balun 11 interposedtherebetween.

In this way, the difference between the noise received at one outputterminal of the balun 11 from the DC-DC converter 16 and the noisereceived at the other output terminal of the balun 11 from the DC-DCconverter 16 is reduced to a value within a predetermined allowablerange (ideally, reduced to the extent that there is virtually nodifference). Thus, the noise from the DC-DC converter 16 is sufficientlyreduced by the compensation of the in-phase component using the balun11. As a result, the wireless communication system SYS1 can prevent thedegradation of the reception sensitivity of the high frequency signal ata specific frequency (which is an integral multiple of the switchingfrequency).

Note that it is desirable that the distance between the partial powersupply voltage line W21 and the balun 11 and the distance between thepartial power supply voltage line W22 and the balun 11 are substantiallythe same. More specifically, it is desirable that the distance betweenthe partial power supply voltage line W21 and the outer periphery of thecoils L11 and L12 that configure the balun 11, and the distance betweenthe partial power supply voltage line W22 and the outer periphery of thecoils L11 and L12 that configure the balun 11 are substantially thesame. Here, the phrase “substantially the same” means not only the casein which the two distances are completely equal to each other, but alsothe case in which the two distances deviate from the state of beingcompletely equal by an error. With this configuration, the magnitude ofthe noise received at one output terminal of the balun 11 from the DC-DCconverter 16 and the magnitude of the noise received at the other outputterminal of the balun 11 from the DC-DC converter 16 is further reduced.As a result, the degradation of the reception sensitivity of the highfrequency signal is further reduced at a specific frequency of thewireless communication system SYS1 b.

Also it is desirable that the width of the partial power supply voltageline W21 and the width of the partial power supply voltage line W22 aresubstantially the same. In addition, it is desirable that the partialpower supply voltage line W21 and the partial power supply voltage lineW22 are arranged symmetrically with respect to the balun 11 (with theX-X′ axis as the symmetry axis). In this way, the difference between themagnitude of the noise received at one output terminal of the balun 11from the DC-DC converter 16 and the magnitude of the noise received atthe other output terminal of the balun 11 from the DC-DC converter 16 isfurther reduced. As a result, the degradation of the receptionsensitivity of the high frequency signal is further reduced at aspecific frequency of the wireless communication system SYS1 b.

Third Embodiment

FIG. 6 is a block diagram showing a configuration example of a wirelesscommunication system SYS2 according to a third embodiment. Although thecircuit of the reception path is mainly shown in the wirelesscommunication system SYS1, the circuit of the transmission path ismainly shown in the wireless communication system SYS2. A detaileddescription is given below.

As shown in FIG. 6, the wireless communication system SYS2 includes atleast a wireless communication device (semiconductor device) 2 and anantenna A2. For example, the wireless communication device 2 is formedon a single semiconductor chip, including a balun 21, a power amplifier(internal circuit) 22, a demodulation unit 23, a DA converter 24, and abaseband processing unit 25. Note that in the example of FIG. 6, thecircuit of the transmission path is shown in the wireless communicationdevice 2 but, of course, the circuit of the reception path can beprovided in the wireless communication device 2.

The baseband processing unit 25 generates a baseband signal based on thedata received from the upper device not shown. The DA converter 24converts the digital baseband signal into an analog baseband signal. Thedemodulation unit 23 demodulates the analog baseband signal output fromthe DA converter 24 into a differential high frequency signal. The poweramplifier 22 amplifies the differential high frequency signal outputfrom the demodulation unit 23, to a level sufficient for wirelesstransmission.

For example, the balun 21 converts the differential high frequencysignal output from the power amplifier 22 into a single-ended highfrequency signal. Note that the balun 21 not only converts thesingle-ended high frequency signal into a differential high frequencysignal, but also outputs a differential high frequency signal bytransmitting the differential high frequency signal in some cases.Hereinafter, only the former case will be described as a representativeexample.

More specifically, the balun 21 is configured with a primary coil L22and a secondary coil L21. One end of the primary coil L22 is coupled toa non-inverting output terminal (P-side terminal) of the power amplifier22, and the other end of the primary coil L22 is coupled to an invertingoutput terminal (N-side terminal) of the power amplifier 22. One end ofthe secondary coil L21 is coupled to the antenna A2 and the other end ofthe secondary coil L21 is coupled to the ground voltage terminal GND.

For example, when the wirelessly transmitted high frequency signal has apositive amplitude, the current flows from one end to the other end ofthe primary coil L22. Then, a positive electromotive force is generatedin the secondary coil L12 according to the current change in the primarycoil L22. On the other hand, when the wirelessly transmitted highfrequency signal is a negative amplitude, the current flows from theother end to one end of the primary coil L22. Then, a negativeelectromotive force is generated in the primary coil L21 according tothe current change in the primary coil L22. As a result, a negativeamplitude AC signal is generated at one end of the secondary coil L21.In other words, a single-ended high frequency signal is output from oneend of the secondary coil L21.

Note that the configuration of the balun 21 is not limited to theconfiguration described above, but can be appropriately applied to anyother configurations with an equivalent function. For example, inaddition to performing the conversion between balance and imbalance ofelectrical signals, the balun 21 may have a function as a matchingcircuit that performs impedance matching.

The single-ended high frequency signal output from the balun 21 iswirelessly transmitted to the outside through the antenna A2.

The DC-DC converter 26 corresponds to the DA converter 16 and has aswitching circuit configuration. The DC-DC converter 26 performs aswitching operation synchronously with a clock signal CLK (not shown) togenerate an output voltage Vout by stepping up or down an input voltageVin that is supplied from a power source (not shown). The output voltageVout is supplied to the respective functional blocks (the poweramplifier 22, the demodulation unit 23, the DA converter 24, thebaseband processing unit 25, and the like) that are provided in thewireless communication device 2.

In this way, the wireless communication system SYS2 drives eachfunctional block by using the output voltage Vout from the DC-DCconverter 26, thus causing current to be intermittently supplied fromthe power source. As a result, the increase in power consumption can besuppressed.

Next, the planar structure of the wireless communication system SYS2 isdescribed.

(Planer Structure of the Wireless Communication System SYS2 According tothe Third Embodiment)

FIG. 7 is a schematic plan view of the wireless communication systemSYS2 according to the third embodiment.

As shown in FIG. 7, in the wireless communication system SYS2, thesemiconductor package 101 (corresponding to the wireless communicationdevice) is formed on the board 100. The tab ground 102, which is thecommon ground voltage area, is formed within the semiconductor package101. Then, the semiconductor chip 103 is formed on the tab ground 102.Note that the tab ground 102 is coupled to the ground voltage source GNDthrough the board 100.

A plurality of functional blocks and a plurality of pads are arranged onthe semiconductor chip 103. In the example of FIG. 7, of the functionalblocks, only the balun 21, the low noise amplifier 22, the demodulationunit 23, the DA converter 24, the baseband processing unit 25, and theDC-DC converter 26 are shown, and similarly of the pads, only pads PDV2,PDG2, PDG 21 to PDG22, PDP2, and PDN2 are shown.

The pads are arranged along the outer periphery on the semiconductorchip 103. The balun 21 is provided as close to the outer periphery aspossible on the semiconductor chip 103. In this way, the balun 21 canwirelessly transmit the high frequency signal with a high sensitivity.

As described above, the balun 21 is configured with the primary coil L22and the secondary coil L21. In the example of FIG. 7, the primary coilL22 and the secondary coil L21 are arranged in a whorl-like pattern insuch a way that their outer periphery is rectangular in the same wiringlayer (however, in different wiring layers at the intersection).Further, in the example of FIG. 7, the primary coil L22 and thesecondary coil L21 are arranged symmetrically with respect to the X-X′axis as the symmetry axis.

One end of the secondary coil L21 is coupled to the pad PDP2 and theother end of the secondary coil L21 is coupled to the pad PDN2. The padPDP2 is coupled to an external connection terminal P2 of thesemiconductor package 101 through a bonding wire BWP2. The externalconnection terminal P2 is coupled to the antenna A2 through the board100. The pad PDN2 is coupled to an external connection terminal N2 ofthe semiconductor package 101 through the bonding wire BWN2. Then, theexternal connection terminal N2 is coupled to the ground voltage sourceGDN through the board 100.

One end of the primary coil L22 is coupled to the non-inverting outputterminal (P-side terminal) of the power amplifier 22. Then, the otherend of the primary coil L22 is coupled to the inverting output terminal(N-side terminal) of the power amplifier 22.

Further, a ground voltage line W3 is provided on the semiconductor chip103 to couple the power amplifier 22 and the ground voltage source GND.More specifically, the ground voltage line W3 is arranged to extend fromthe voltage terminal on the low potential side of the power amplifier 22towards the pads PDG21 to PDG22 around the balun 21.

The pads PDG21 to PDG22 are coupled to the tab ground 102, which is thecommon ground voltage area within the semiconductor package 101,respectively, through the bonding wires BWG21 to BWG22.

The voltage terminal on the high potential side of the DC-DC converter26 is coupled to the pad PDV2. Further, the voltage terminal on the lowpotential side of the DC-DC converter 26 is coupled to the pad PDG2. Thepad PDV2 is coupled to an external connection terminal V2 of thesemiconductor package 101 through a bonding wire BWV2. The externalconnection terminal is coupled to the power supply voltage source VDDthrough the board 100. The pad PDG2 is coupled to an external connectionterminal G2 of the semiconductor package 101 through the bonding wireBWG2. Then, the external connection terminal G2 is coupled to the groundvoltage source GND through the board 100.

Here, of the wiring paths from the power amplifier 22 to the pads PDG21to PDG22 around the balun 21, the ground voltage line W3 is located in afirst path (a path on the side closer to the outer periphery of thechip) passing through one side of the balun 21. At the same time, theground voltage line W3 is also branched into a second path (a path onthe side farther from the outer periphery of the chip) passing throughthe other side of the balun 21.

Hereinafter, the ground voltage line W3 located in the first pathpassing through one side of the balun 21 will be referred to as apartial ground voltage line W31, and the ground voltage line W3 locatedin the second path passing through the other side of the balun 21 willbe referred to as a partial ground voltage line W32. At this time, thepartial voltage lines W31 and W32 are arranged to face each other withthe balun interposed therebetween.

In other words, the ground voltage line W3 including the partial groundvoltage lines W31, W32 as well as the power amplifier 22 are provided tosurround the balun 21. Here, a joint part Q2 of the ground voltage lineW3 in which ground voltages supplied through the pads PDG21 to PDG22 aregathered is located outside the line part of the ground voltage line W3surrounding the balun 21. At the same time, the joint part Q2 is locatedon the symmetry axis (on the X-X′ axis) of the balun 21.

With this configuration, the difference between the noise received atone output terminal (one end of the secondary coil L21) of the balun 21from the DC-DC converter 26 and the noise received at the other terminal(the other end of the secondary coil L21) of the balun 21 from the DC-DCconverter 26 is reduced to a value within a predetermined allowablerange (ideally, reduced to the extent that there is virtually nodifference). Thus, the wireless communication system SYS2 can preventthe degradation of the reception sensitivity of the high frequencysignal at a specific frequency (which is an integral multiple of theswitching frequency).

FIG. 8 is a schematic plan view showing the propagation of the noisefrom the DC-DC converter 26 to the balun 21 in the wirelesscommunication system SYS2.

As shown in FIG. 8, the partial ground voltage lines W31 and W32 arearranged to face each other with the balun 21 interposed therebetween.With this configuration, the electromagnetically coupling strengthbetween each of the partial ground voltage lines W31, W32 and thepositive side (the path on one end side of each of the coils L21 andL22) of the balun 21 and the electromagnetically coupling strengthbetween each of the partial ground voltage lines W31, W32 and thenegative side (the path on the other side of each of the coils L21 andL22) of the balun 21 are approximately equal to each other. In this way,the difference between the magnitude of the noise received at one outputterminal of the balun 21 from the DC-DC converter 26 and the magnitudeof the noise received at the other output terminal of the balun 21 fromthe DC-DC converter 26 is reduced to a value within a predeterminedallowable range. Thus, the noise from the DC-DC converter 26 issufficiently reduced by the compensation of the in-phase component usingthe balun 21. As a result, the wireless communication system SYS2 canprevent the degradation of the reception sensitivity of the highfrequency signal at a specific frequency (which is an integral multipleof the switching frequency).

Note that it is desirable that the distance between the partial groundvoltage line W31 and the balun 21 and the distance between the partialground voltage line W32 and the balun 21 are substantially the same.More specifically, it is desirable that the distance between the partialground voltage line W31 and the outer periphery of the coils L21 and L22that configure the balun 21, and the distance between the partial groundvoltage line W32 and the outer periphery of the coils L21 and L22 thatconfigure the balun 21 are substantially the same. Here, the phrase“substantially the same” means including not only the case in which thetwo distances are completely equal to each other, but also the case inwhich the two distances deviate from the state of being completely equalby an error. With this configuration, the difference between themagnitude of the noise received at one output terminal of the balun 21from the DC-DC converter 21 and the magnitude of the noise received atthe other output terminal of the balun 21 from the DC-DC converter 21 isfurther reduced. Thus, the degradation of the reception sensitivity ofthe high frequency signal is further reduced at a specific frequency ofthe wireless communication system SYS2.

Also it is desirable that the width of the partial ground voltage lineW31 and the wide of the partial ground voltage line W32 aresubstantially the same. In addition, it is desirable that the partialground voltage line W31 and the partial ground voltage line W32 arearranged symmetrically with respect to the balun 21 (with the X-X′ axisas the symmetry axis). In this way, the difference between the magnitudeof the noise received at one output terminal of the balun 21 from theDC-DC converter 26 and the magnitude of the noise received at the otheroutput terminal of the balun 21 from the DC-DC converter 26 is furtherreduced. Thus, the degradation of the reception sensitivity of the highfrequency signal is further reduced at a specific frequency of thewireless communication system SYS2.

As described above, in the wireless communication system SYS2, not onlythe balun 21 and the power amplifier 22 but also the DC-DC converter 26is mounted on the semiconductor chip 103 forming the wirelesscommunication device 2. Further, the ground voltage line W3 that couplesthe power amplifier 22 to the ground voltage source GND is branched intothe partial ground voltage lines W31 and W32. Then, the partial groundvoltage lines W31 and W32 are arranged to face each other with the balun21 interposed therebetween. With this configuration, the wirelesscommunication system SYS2 can make the magnitudes of the noises receivedat one output terminal and the other output terminal of the balun 11from the DC-DC converter 16 approximately equal to each other, therebyreducing the degradation of the reception sensitivity of the highfrequency signal at a specific frequency.

As described above, in each wireless communication system according tothe first to third embodiments, not only the balun and the amplifier(the low noise amplifier, the power amplifier, or the like) but also theDC-DC converter is mounted on the semiconductor chip forming thewireless communication system. Further, the ground voltage line thatcouples the amplifier to the ground voltage source is branched into twopartial ground voltage lines. Then, the partial ground voltage lines arearranged to face each other with the balun interposed therebetween. Withthis configuration, each wireless communication system according to thefirst to third embodiments can make the magnitudes of the noises, whichare received at one output terminal and the other output terminal of thebalun from the DC-DC converter, approximately equal to each other,thereby reducing the degradation of the reception sensitivity of thehigh frequency signal at a specific frequency.

The invention made by the present inventors has been specificallydescribed based on the embodiments. However, it is needless to say thatthe present invention is not limited to the foregoing embodiments andvarious modifications and alterations can be made within the scope notdeparting from the gist of the present invention.

For example, in each semiconductor device according to the exemplaryembodiments, the conductivity type (P type or N type) of thesemiconductor substrate, the semiconductor layer, the diffusion layer(diffusion area) or other layers can be reversed. Thus, if it is assumedthat one conductivity type, either N type or P type, is a firstconductivity and the other conductivity type is a second conductivity,it is possible to define the first conductivity type as P type and thesecond conductivity type as N type or, inversely, define the firstconductivity type as N type and the second conductivity type as P type.

What is claimed is:
 1. A semiconductor device comprising a semiconductorchip, wherein the semiconductor chip includes: a switching-type DC-DCconverter; a pad for receiving a high frequency signal from an antenna;a balun connected to the pad and configured with a coil to output adifferential signal based on the high frequency signal; an internalcircuit driven by an output voltage of the DC-DC converter to processthe differential signal output from the balun; and a ground voltage linethat couples the internal circuit to a ground voltage source, whereinthe ground voltage line comprises: a first partial ground voltage line;and a second partial ground voltage line arranged to face the firstpartial ground voltage line with the balun interposed therebetween. 2.The semiconductor device according to claim 1, wherein a distancebetween the first partial ground voltage line and an outer periphery ofthe coil configuring the balun and a distance between the second partialground voltage line and the outer periphery of the coil configuring thebalun are substantially the same.
 3. The semiconductor device accordingto claim 1, wherein a width of the first partial ground voltage line anda width of the second partial ground voltage line are substantially thesame.
 4. The semiconductor device according to claim 1, wherein thefirst partial ground voltage line and the second partial ground voltageline are arranged symmetrically with respect to the balun.
 5. Thesemiconductor device according to claim 1, further comprising a powersupply voltage line through which the output voltage of the DC-DCconverter is propagated from the DC-DC converter to the internalcircuit, wherein the power supply voltage line comprises: a firstpartial power supply voltage line; and a second partial power supplyvoltage line arranged to face the first power supply voltage line withthe balun interposed therebetween.
 6. The semiconductor device accordingto claim 5, wherein the first and second partial power supply voltagelines are arranged in such a way that a difference between a noisereceived at one output terminal of the balun from the DC-DC converterand a noise received at another output terminal of the balun from theDC-DC converter is within a predetermined allowable range.
 7. Thesemiconductor device according to claim 5, wherein the first and secondpartial power supply voltage lines are arranged in such a way that thereis virtually no difference between a noise received at one outputterminal of the balun from the DC-DC converter and a noise received atanother output terminal of the balun from the DC-DC converter.
 8. Thesemiconductor device according to claim 5, wherein a distance betweenthe first partial power supply voltage line and an outer periphery ofthe coil configuring the balun and a distance between the second powersupply voltage line and an outer periphery of the coil configuring thebalun are substantially the same.
 9. The semiconductor device accordingto claim 5, wherein a width of the first partial power supply voltageline and a width of the second partial power supply voltage line aresubstantially the same.
 10. The semiconductor device according to claim5, wherein the first partial power supply voltage line and the secondpartial power supply voltage line are arranged symmetrically withrespect to the balun.
 11. The semiconductor device according to claim 1,wherein the internal circuit comprises a low noise amplifier thatamplifies the differential signal.
 12. A power measurement devicecomprising a semiconductor device comprising a semiconductor chip,wherein the semiconductor chip includes: a switching-type DC-DCconverter; a pad for receiving a high frequency signal from an antenna;a balun connected to the pad and configured with a coil to output adifferential signal based on the high frequency signal; an internalcircuit driven by an output voltage of the DC-DC converter to processthe differential signal output from the balun; and a ground voltage linethat couples the internal circuit to a ground voltage source, whereinthe ground voltage line comprises: a first partial ground voltage line;and a second partial ground voltage line arranged to face the firstpartial ground voltage line with the balun interposed therebetween.